Is there a way to determine why Blender is running so slow?
Another guess would be that it could be an issue with the hardware. Perhaps the CPU is having a hard time because of the number of cores? Another possible theory is that there are other programs in the background taking up all of the extra resources to speed things along. Another possibility is that the number of vertices in the scene is high that it lags. You may have to, as neighborlee suggested, to do something to reduce the high poly count.